Many work machines, particularly earth working machines, use a hydrostatic drive system to drive the traction wheels or tracks of the work machine. The hydrostatic drive system can provide a continuously variable speed output to the wheels or tracks of the work machine. In particular, the speed can be continuously varied by controlling the displacements of either a hydraulic pump or a hydraulic motor which comprise the hydrostatic drive system.
One problem with earth moving machines which use hydrostatic transmissions is that the speed output can be varied rapidly thereby producing a rapid response. This rapid response can result in high, undesirable jerk which can cause discomfort to an operator of the work machine. In addition, the undesirable high jerk can cause the operator to lose control of the machine as the rapid movement of the machine can create unwanted speed pedal modulations. The unwanted speed pedal modulations create control signals which cause the work machine to move in an unintended manner.
However, in some situations the operator may decide to drastically change the desired velocity by rapidly changing the position of the pedal. In such cases, the operator generally wants a high jerk because he has commanded the rapid change in desired velocity. If the apparatus used to generate velocity commands is biased to provide a slow smooth response, then the resulting change in the commanded velocity will seem extremely slow to the operator of the work machine. Even if the operation of the work machine is set to respond with a relatively high jerk, the work machine may not respond rapidly enough to provide the operator with the sensation that the work machine is responding rapidly to the drastic changes commanded by the operator.
What is needed therefore is a method and apparatus for generating velocity commands in response to rapid changes in operator inputs which overcomes the above-mentioned drawbacks.